title: Nitrogen deposition alters plant-fungal relationships: linking belowground dynamics to aboveground vegetation change.
abstract: Nitrogen (N) deposition rates are increasing globally due to anthropogenic activities. Plant community responses to N are often attributed to altered competitive interactions between plants, but may also be a result of microbial responses to N, particularly root-associated fungi (RAF), which are known to affect plant fitness. In response to N, Deschampsia cespitosa, a codominant plant in the alpine tundra at Niwot Ridge (CO), increases in abundance, while Geum rossii, its principal competitor, declines. Importantly, G. rossii declines with N even in the absence of its competitor. We examined whether contrasting host responses to N are associated with altered plant-fungal symbioses, and whether the effects of N are distinct from effects of altered plant competition on RAF, using 454 pyrosequencing. Host RAF communities were distinct (only 9.4% of OTUs overlapped). N increased RAF diversity in G. rossii, but decreased it in D. cespitosa. D. cespitosa RAF communities were more responsive to N than G. rossii RAF communities, perhaps indicating a flexible microbial community aids host adaptation to nutrient enrichment. Effects of removing D. cespitosa were distinct from effects of N on G. rossii RAF, and D. cespitosa presence reversed RAF diversity response to N. The most dominant G. rossii RAF order, Helotiales, was the most affected by N, declining from 83% to 60% of sequences, perhaps indicating a loss of mutualists under N enrichment. These results highlight the potential importance of belowground microbial dynamics in plant responses to N deposition.
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, USA.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Dean
authors.affiliation: Department of Environmental Science, Policy & Management, University of California, Berkeley, CA, USA.
authors.forename: Emily C
authors.initials: EC
authors.lastname: Farrer
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, USA.|Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, USA.
authors.forename: D Lee
authors.initials: DL
authors.lastname: Taylor
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, USA.|Department of Biological Sciences, Western Illinois University, Macomb, IL, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Porras-Alfaro
authors.affiliation: Department of Environmental Science, Policy & Management, University of California, Berkeley, CA, USA.
authors.forename: Katharine N
authors.initials: KN
authors.lastname: Suding
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sinsabaugh
mesh_terms: D003120:Colorado; D004271:DNA, Fungal / Q000235:genetics; D017753:Ecosystem; D005658:Fungi / Q000502:physiology*; D031986:Geum / Q000382:microbiology*; D008957:Models, Genetic; D009584:Nitrogen / Q000737:chemistry*; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology; D006109:Poaceae / Q000502:physiology*; D017422:Sequence Analysis, DNA; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013559:Symbiosis
chemical_list: D004271:DNA, Fungal; D012987:Soil; D009584:Nitrogen
keywords: 454 pyrosequencing; Helotiales; ITS; endophytes; nitrogen deposition; root fungi